1. Field of the Invention
The present invention relates to a novel process for preparing tricyclic-heterocycles which are useful as intermediates for the preparation of cardiovascular agents. The tricyclic heterocyclic compounds prepared by this process are useful in treating conditions where decreased vasopressin levels are desired, such as in congestive heart failure, and in other disease conditions characterized by excess renal water reabsorption, and in conditions with increased vascular resistance and coronary vasoconstriction.
2. Background of the Invention
Vasopressin is released from the posterior pituitary either in response to increased plasma osmolarity detected by brain osmoreceptors or decreased blood volume and blood pressure sensed by low-pressure volume receptors and arterial baroreceptors. The hormone exerts its actions through two well defined receptor subtypes: vascular V.sub.1 and renal epithelial V.sub.2 receptors. Vasopressin-induced antidiuresis, mediated by renal epithelial V.sub.2 receptors, helps to maintain normal plasma osmolarity, blood volume and blood pressure.
Vasopressin is involved in some cases of congestive heart failure where peripheral resistance is increased. V.sub.1 antagonists may decrease systemic vascular resistance, increase cardiac output and prevent vasopressin induced coronary vasoconstriction. Thus, in conditions with vasopressin induced increases in total peripheral resistance and altered local blood flow, V.sub.1 -antagonists may be therapeutic agents. V.sub.1 antagonists may decrease blood pressure, and thus be therapeutically useful in treatment of some types of hypertension.
The blockade of V.sub.2 receptors is useful in treating diseases characterized by excess renal reabsorption of free water. Antidiuresis is regulated by the hypothalamic release of vasopressin (antidiuretic hormone) which binds to specific receptors on renal collecting tubule cells. This binding stimulates adenylyl cyclase and promotes the cAMP-mediated incorporation of water pores into the luminal surface of these cells. V.sub.2 antagonists may correct the fluid retention in congestive heart failure, liver cirrhosis, nephrotic syndrome, central nervous system injuries, lung disease and hyponatremia.
Elevated vasopressin levels occur in congestive heart failure which is more common in older patients with chronic heart failure. In patients with hyponatremic congestive heart failure and elevated vasopressin levels, a V.sub.2 antagonist may be beneficial in promoting free water excretion by antagonizing the action of antidiuretic hormone. On the basis of the biochemical and pharmacological effects of vasopressin, antagonists of vasopressin, which may be made in accordance with the process of this invention, are expected to be therapeutically useful in the treatment and/or prevention of hypertension, cardiac insufficiency, coronary vasospasm, cardiac ischemia, renal vasospasm, liver cirrhosis, congestive heart failure, nephrotic syndrome, brain edema, cerebral ischemia, cerebral hemorrhage-stroke, thrombosis-bleeding and abnormal states of water rentention.
Premature birth can cause infant health problems and mortality and a key mediator in the mechanism of labor is the peptide hormone oxytocin. On the basis of the pharmacological action of oxytocin, antagonists of this hormone are useful in the prevention of preterm labor, B. E. Evans et al., J. Med. Chem. 35, 3919 (1992), J. Med. Chem. 36, 3993 (1993) and references therein. The compounds made by the process of this invention are antagonists of the peptide hormone oxytocin and are useful in the control of premature birth.
The present invention relates to a novel process to prepare tricyclic derivatives which exhibit antagonist activity at V.sub.1 and/or V.sub.2 receptors and exhibit in vivo vasopressin antagonist activity. The compounds also exhibit antagonist activity at oxytocin receptors.